Almost all modern automotive engines have an electronic exhaust gas recirculation valve (EEGR valve) to recycle a portion of the exhaust gases of the engine into the intake air stream of the engine. The exhaust gases, especially those from spark-ignition gasoline engines, include a substantial amount of incomplete combustion products, including unburned fuel, oxides of nitrogen and other compounds. These gases contribute substantially to air pollution. EGR valves, and the more recent EEGR valves were installed on automotive engines to reduce this exhaust gas pollution by recycling a portion of the exhaust gases back into the intake air stream, thereby recombusting the exhaust gases and reducing pollution.
The EGR valves are subjected to severe environmental conditions that cause premature failure and require premature replacement. EGR valves are located in the engine compartments of automobiles and are typically mounted directly on the engine. As a result, they are subjected to extremes in temperature due to thermal conduction and convection from the engine, and due to the extremely hot exhaust gas stream that they are designed to throttle. Engine compartment temperatures commonly vary from -20C to 160C. In addition to thermal stresses, EGRs are subject to extreme vibration as they are directly mounted to automobile engines that vibrate. Finally, since the underside of most automobiles are not enclosed, the engine compartment air is often filled with dirt, dust, oil, chemical vapours, moisture and road salt. All of these factors cause the premature failure of EGRs and necessitate their premature replacement.
Electronic EGR valves are particularly subject to premature failure due to their design. Modern EEGR valves are unlike earlier EGR valves in that they use an electrical actuator, typically a linear solenoid to open the valve itself instead of the older and more robust diaphragm arrangement of earlier EGRs. As a result EEGRs have more parts to fail, they require tighter tolerances to operate properly, and they have more sliding surfaces that can rapidly wear due to fouling by contaminants such as oil, dirt, dust and the like. In addition, the thermal extremes cause uneven expansion and contraction which can cause components to bind rather than slide with respect to each other. Linear solenoids are particularly subject to damage due to the relatively large diameter of the solenoid armatures (the moving part of the solenoid) and the relatively large excursion of the armature required to fully open the valve itself. As a result, they have large surface areas in sliding contact and correspondingly large bearings.
It is the purpose of this invention to provide a novel means of supporting the armature of an EEGR valve that reduces the premature EEGR wear and failure by reducing the amount of sliding contact between the armature and the stator.